A silicon carbide (SiC) Schottky diode having resistance to high voltages on the order of kV is configured of an n-type epitaxial layer constituted of SiC and a Schottky electrode formed thereon. In this structure, electric field is apt to concentrate at the periphery of the joint surface between the epitaxial layer and the Schottky electrode. It is therefore necessary that a p-type termination structure for alleviating the electric-field concentration should be formed on a surface layer of the periphery of the joint surface (Schottky joint surface).
For forming the p-type termination structure, a method, in which ions of a p-type impurity such as Al (aluminum) or B (boron) are implanted in an n-type epitaxial layer and activation annealing is performed to the layer through a high-temperature heat treatment at about 1,500° C. or higher, is generally used. For forming a Schottky junction having satisfactory properties, it is necessary to remove the altered layer which has been formed in the SiC surface as a result of the high-temperature heat treatment. Known as techniques for removing the altered layer are, for example, the techniques described in patent documents 1 to 3.
Patent document 1 describes, as a technique for removing the altered layer, a technique in which sacrificial oxidation is performed to a surface layer of the SiC after the activation annealing to form a sacrificial oxide film having a thickness of 40 nm or more but less than 140 nm as a surface layer, and the altered layer is removed together with the sacrificial oxide film.
Patent document 2 describes a technique in which a native oxide film is removed by a treatment with hydrofluoric acid and the surface of the SiC is subsequently cleaned by etching with plasma of a hydrogen/oxygen mixture gas or plasma of a gas containing fluorine atoms.
Patent document 3 describes that an altered layer having a thickness of about 100 nm generates and the altered layer having a thickness of about 100 nm is removed by etching or polishing in an atmosphere containing hydrogen.